Refrigeration system including defrosting apparatus



Man-ch10, 1959 c. BOLING 2,876,630 4 REFRIGERATION SYSTEM INCLUDINGDEFROSTINC APPARATUS Filed Febjls, 1955 /08 I k? g4, 2

INVENTOR eel ll B06611;

, ATTORN s 5 Sheets- Sheet 1 March 10, 1959 C. BOLING REFRiGERATIONSYSTEM mcwnmc DEFROSTING APPARATUS Filed Feb. 18, 1955.

5 Sheets-Sheet 4 lg l March 10, 1959 c. BOLING 2,876,630 I REFRiGERATIONSYSTEM INCLUDING'FDEFROSTING APPARATUS} l' i led Feb. 18, 1955 5Shegts-Sheet 5 ATTORNE Unite REFRIGERATION SYSTEM INCLUDING DEFROSTINGAPPARATUS Application February 18,1955, Serial N 0. 489,074

12 Claims. (Cl. 62-234)" This" invention relates to refrigeration,andr'n'ore in particular to defrosting refrigeration systems of the-typewhich are adapted to maintain refrigerated compartments at low'temperatures, for example, considerably below freezing. 7

An object of this invention is to provide refrigeration systems whichmay be defrosted in an improved manner. Another object is to providerefrigeration systemsgwhich a re'superior to prior systems for certaintypes of applications and which are adaptable to various conditions ofnseand ope'ration'. A further objectis to provide an improvedarrangement for defrosting low temperature evaporaters. A still furtherobject'is to provide refrigeration systemswhichare defrosted with theuse of hot refrigerant in an improved manner. A further object is toprovide such systems which-require the use of a' minimum numberofcomponents and parts. A further objectis to provide systems of the abovecharacter which occupy minimum space and which are provided withcomponents which arestur'dy in construction, efiicient and dependablein' use, and which are adaptable to meet various demandsand'practice's.These and other objects will be in part obvious and in part pointedoutbelow.

In the drawings:

Figure 1 is a somewhat schematic representation of one ernbodinient'ofthe invention; I

Figure 2 is" a rear elevation of the evaporator assembly ornigure' 1; v

Figure? is a side'elevation of the assembly of Figure 2;

Figure 4 is a sectionalview with the central portion broken away on theline 44 of Figure 3;.

Figure 5 is a' side elevation of the evaporator unit of Figure 4 withthe associated parts;

Figure 6 is a sectional view on the line 6-6 of Figure 4; I, Figure-7 isa" schematic representation of the refrigerant flowiri" thes'ystern ofFigure 1 during. the defrostingopstation; and,

States Patent 0 I 2,876,630 Patented Mar. 10, 1959 through a line 32anda constant pressure expansionvalve 34 to line. 19.

EvaporatorZDis constructed, as shown best in Figures 4,5, and 6 of threevertical rows. of evaporator tube as semblie's-36 which are identical inconstruction. Each of the'tubeassemblies'36 is formed by an outertube'38 (see also Figure 8') an inner tube wand an internal fin assembly42. Hence, each tube has an internal refrigerant passageway 44 withintube 40 and an annular refrigerant passageway 46 between tubes 38 and'40, and the fin assembly 42 is positioned" within this annularpassageway.

An external fin assembly 48 is provided ontubes'38. This.

assembly of tubes 38 and 40 and finas'sem'bly 42 is'constructed inaccordance with the disclosure of my copending'ap'plication, Serial No.310,820, filed September 22, 1952, and incorporates certain features ofthe iniventions of my prior U. S. Patents Nos; 2,611,585 and 2,611,587.The fin assembly comprises a corrugated strip of sheet metal positionedspirally in space 46, and after assembly of tube 4il'a'nd fin assembly42 within tube38, the inner'tube 4i isexpanded to place the fin assemblyunder uniform'radial compression between the concentric tube walls.Hence, good heat transfer relationships are provided between fluids ineach of the passageways 44 and 46and the external fin assembly 48. Theheat transfer'relationship between. the fluid in passageway 46 and theexternal fin assembly is through the internal fin assembly 42 andtube38, and the fluid in passageway'44 is in good heat transferrelationship through tube 40 with fin assembly'42, and thence throughtube 38 to the fin assembly 48. Hence, refrigerant in either ofpassageways 46 or 44'isin good heat transfer relationship with theexternal fin assembly.

As indicated above, in this embodiment of the invention three verticalrows of tube assemblies 36 are arranged in eight horizontally positionedgroups of three tubes each. For convenience, the vertical rows areindicated at 50, 52, and 54', and the eight horizontal rows areindicated at 56, 58, 60, 62, 64, 66, 68, and 70. The refrigerantdistributor assembly 24 has four distributor tubes 72, 74, 76;, and 7 8ext'endingLto the tube assemblies 36in the left-hand" vertical row 56,and respectively in the alternate horizontal rows 68, 64, 60 and 56.Each ofthese distributor tubes is connected through the wall of theouter tube 38 of its tube assembly as shown in Figure 6, so that theliquid refrigerant is delivered to the annular passageway 46. An annularcover or cap 80 closes" the Figure 8 is an enlarged sectional view onthe line 88 of Figure 6. I

Referring particularly to Figure l, the refrigeration system hasa'compressor 4, a condenser 10, a receiver 12, and an evaporator 20.Compressor 4' is driven by. a motor 6, and delivers hot compressedrefrigerant gas through'a line S to condenser 10. The liquid-refrigerantflo'wsfrom' thec'o'ndenser info receiver 12- which is connected' to theevaporator through a line 14,- theliquid circuit of a heat exchanger 16,a line 18, an expansion valve 22, and a line 19. The refrigerant isdelivered to the" various;s.'e' ';tionsof the evaporator through adistributor assembly 24'.

The evaporator is connected through a gas returnline 26, having. the gascircuit of the heat exchanger 16-therein,

back to the compresser 4. The hot gas line 8 is connected I mannerdescribed below. Evaporator 20 is connected adjacent end of this annularpassageway.

The opposite end of this annular passageway is con nected through aU-tube 82' to the adjacent end of the annular passageway in the tubeassembly in the same horizontal row and in the next vertical row 52.Similarly, the opposite end of this annular passagewayis connectedthrough a U-tube 84 to the annular passageway of the other tube assemblyin that horizontal row, i. e., in the vertical row 54. The opposite endof that annular passageway'is connected through a vertical U-tube 86(see Figure 4*) to the annular passageway in the tube assembly directlyabove it, i; e., in the next higher horizontal row but in-thesame'vertical row 54. The three tubes of each horizontal row' have theirannular passageway interconnected by a=pair of U-tubes similar to 82 and84, as ex plained above. The end of each annular passagewaydire'ctlyabove the one to which a distributor tube'is attached is connectedthrough a U'-tube 88 to a refrigerant outlet or gas header 90. Hence,the annular passageways for the two bottom rows 56 and 58 of tubeassemblies are connected in a series circuit between the liquiddistributor tube-78 and a U-tube88 which discharges into header90. Theannular passageways of the tube assemblies of each ofthe pairs of rows,60" and 62, 64* and 6'6, and 68- and are similarly connected. Hence, inthis embodiment,

' during the defrosting operations.

3 there are four evaporator circuits connected in parallel, receivingliquid refrigerant through the distributor tubes and dischargingrefrigerantfgas into header 90.

Each of the inner tubes 40 extends beyond the con nection to the annularpassageway around it, and all of theseinner tubes 40 of the tubeassemblies in each of the vertical rows are connected in series betweena bottom header (Figures 4 and 5) 92 and an upper header 94. The bottomtube 40 opens directly into header 92, and its opposite end is connectedthrough a U-tube 96 to the inner tube 40 of the next higher tubeassembly. Identical U-tubes 96 connect each similar tube end to thenext, and the right-hand end of the top tube 40 opens into the topheader 94. The'circuits for the tubes 4i) in all of the vertical rowsare identical Header 92 (see Figure 5) is connected directly to the hotgas line 30, and header 94 is connected through a line 32 to theconstant pressure expansion valve 34 which, as indicated above, is

connected to line 19. A control tube 98 extends from header 90 to valve34.

The entire evaporator assembly is rigidly mounted in a pair of endplates 100 (see Figures 2 and 3), and is enclosed within a casing 102.The casing is supported by a pair of channel bars 104 from which a fanmotor 106 with its fan 108 is supported by a bracket 110. A cowl 112 isprovided which has an opening for the passage of air which is blownthrough the coil by the fan. The bottom of casing 102 is formed by adrip pan 114 (Figure 3) which has an electric heater 116 therein to meltthe ice and warm the water which drops into the pan A drain connection(not shown) carries away the condensate as it is melted and collected inpan 114. Air is blown through the unit from the left in Figure 3, and isdeflected upwardly from the face of the unit at the right by a deflector117.

As has been indicated above, the system is operated I to perform acooling operation, for example, to maintain a food-storage compartmentat a selected low temperature. During such operation, frost or frozencondensate in the form of ice accumulates upon the evaporator within theinterstices between the fins, thus interfering with the flow of airthrough the coil, and also interfering with the transfer of heat fromthe air to the refrigerant. During this operation, refrigerant iscondensed in condenser 10, and the liquid refrigerant flows to receiver12 and thence through line 14 to the expansion valve 22. The refrigerantpasses through the expansion valve and line 19 to the distributorassembly 24 which delivers equal streams of refrigerant to the fourevaporator circuits of the evaporator. Each of these circuits is formedby the annular spaces 46 of six of the tube assemblies connected inseries. The gas refrigerant [flows to header 90, and returns throughline 26 to the compressor. During this time, motor 106 operates fan 1'08continuously to circulate air through the coil.

' When sufficient frost or ice is accumulated upon the evaporator tointerfere materially with the cooling of the air, a defrosting operationis initiated. This involves stopping the fan motor 106 so as todiscontinue the circulation of air through the unit and the opening ofsolenoid valve 35 so as to permit the hot compressed gas to flow throughline 30 directly to the evaporator. Simultaneously, the electric heater116 in the drip pan is energized. In Figure 1, an illustrativeelectrical circuit is disclosed for controlling the defrostingoperation.

This circuit includes an adjustable timer 120 which may be set toinitiate the defrosting operation automatically at pre-determinedintervals. The duration of the defrosting operation may also becontrolled.

asvaoso heat from the refrigerant gas within these tubes passes radiallyoutwardly through the tubes 40 (Figure 8), and thence through the finassemblies 42 and tubes 38 to the fin assemblies 43. The heat thustransferred melts the ice free so that particles of ice and condensatewater fall from the evaporator intothe drip pan 114 (Figure 3). The iceparticles are melted and the water is somewhat warmed by the electricheater 116.

The refrigerant within tubes 40 is maintained at an increased pressureby virtue of being connected to the output or high side of thecompressor, and the cooling of the refrigerant at this pressure causesit to condense. The condensed refrigerant flows through header 94, line32, and the expansion valve 34 to line 19. From line 19, it is deliveredthrough distributor assembly 24 to the four evaporator circuits referredto above. The refrigerant is at the reduced pressure of the low" side ofthe compressor so that it is evaporated in the same manner as during thecooling operation, and refrigerant gas is returned to the compressor.During this defrosting operation, the heat from the electric heater unit116 which is not picked up by the melting ice and water tends to heatthe evaporator and increases the rate of defrosting. Furthermore, thehot gas is delivered to the bottom of the evaporator so that the lowertube assemblies are heated first, and this insures that the ice andwater which are freed will not be refrozen onto fin or tube surfaces.

In accordance with the present invention, the heat given off because ofcondensation of the refrigerant within the tube assemblies is readilytransferred through the fin assemblies to the external surfaces. Thisheat is the heat of compression of the system, and is the heat which isdissipated through the condenser during the cooling operation. However,during the defrosting operation this heat is not dissipated but isaccumulated in the evaporator, and the temperature of the evaporatorgradually rises. There is some simultaneous cooling by virtue of theevaporation of the refrigerant, but the heating effect is greater than.the cooling effect so that the evaporator temperature is raised abovethe melting point of water. The fin assemblies 42 permit the free flowof refrigerant through them so that the spaces or passageways 46 providefor the efiicient distribution and evaporation of the refrigerant. Theconnecting of the herizontal rows of tube assemblies in series providesefficient cooling of the air and flow of the refrigerant. The connectingof the tubes 40 of each vertical row of tube assemblies in seriesprovides for eflicient defrosting, even under very adverse conditions ofoperation.

The invention contemplates that the electric heater 116 of theembodiment of the drawings is replaced under some circumstances by atube or line carrying hot refrigerant gas which heats the condensate andice. The invention also contemplates replacing the constant pressureexpansion valve 34 with a fixed orifice or one or more otherrestrictors. Furthermore, under some circumstances the hot refrigerantgas is delivered to the annular passageways 46, rather than to theinternal passageways 44, and then the internal passageways act as there-evaporator. With such an arrangement, the hot gas delivers its heatdirectly through the tubes 38 to the fin assemblies 48, and the liquidrefrigerant is then delivered through a restrictor to the internalpassageways 44. The liquid refrigerant is then re-evaporated asexplained above.

The system herein disclosed provides efiicient defrost ing under varyingconditions of operation. No ex ternal heat source is required, andambient temperatures do not elfect the operation, since the evaporatorand the re-evaporator are a single piece of apparatus positioned withinthe refrigerated space at constant temperature. Hence, the system avoidsthe difliculties which have been encountered with systems which relyupon external heat sources where ambient temperature variations andother conditions cause variations in the length germ-see of timerequired for'defrosting; It'isthus-seen that the present system-may beoperated automatically, withfull assurance that the defrosting will becarried on e'fficien'tly and withoutundesirable heating of theevaporator, which could result from carrying on the defrosting operationfor an excessive period of time. As many possible embodiments may bemade of the mechanicalfeatures of the above invention and as the artherein described might be varied in various parts, all without departingfrom th'escope ofthe invention,-it is to be understood that all matterh'ereinabove set forth, or shown in the accompariying drawings is to beinterpreted as illustrative and not'in a limiting sense.

1; In a refrigeration system of the character described, refrigerantcondensing means comprising compressor means and condenser means, anevaporator assembly comprising a plurality'o'f tubea'ssemblies, each ofwhich has an inner tube and an outer tube positioned concentrically withan annular space therebetween and a fin construction positioned withinsaid annular space and maintained in heat conducting relationship withthe outer surface of the inner tube and the inner surface of the outertube, means interconnecting said inner tubes to form a first passagewaycircuit and interconnecting said annular spaces to form a secondpassageway circuit, means to supply liquid refrigerant at a reducedpressure from said condenser means to one of said passageway circuitswhich then acts as the evaporator space of the system, means to deliverrefrigerant gas from said one of said passageway circuits to the intakeof said compressor, means to defrost said evaporator by supplying hotrefrigerant gas from said compressor to the other of said passagewaycircuits whereby the heat from the compressed gas is transmitted throughsaid fin assemblies and thence through said outer tubes and saidrefrigerant is condensed, and means including restrictor means todeliver the liquid refrigerant from said other of said passagewaycircuits to said one of said passageway circuits at a reduced pressurewhereby the liquid refrigerant is reevaporated and delivered back tosaid compressor.

2. A system as described in claim 1 wherein one of said passagewaycircuits is formed by the annular spaces of the respective tubeassemblies and said other of said passageway circuits is formed by theinternal passageways of the respective inner tubes.

3. Apparatus as described in claim 1 wherein said restrictor means is anexpansion valve.

4. A system as described in claim 1 which includes a drip pan positionedbeneath said tube assemblies and an electric heater positioned withinsaid drip pan and adapted to be energized during the defrostingoperation.

5. A system as described in claim 1 wherein each of said tube assembliesincludes external fins, and wherein said evaporator assembly includes afan which directs a stream of air into heat transfer relationship withsaid fins.

6. A system as described in claim 1 wherein said annular spaces areconnected serially to form a plurality of parallel circuits and saidinner tubes are connected serially to form a plurality of parallelcircuits.

7. A system as described in claim 1 wherein said tube assemblies arepositioned horizontally and there are pluralities of both vertical andhorizontal rows of tube assemblies, wherein the annular spaces in thetube assemblies of each horizontal row are connected in series, andwherein the inner tubes of the tube assemblies of each vertical row areconnected in series.

8. A system as described in claim 7, which includes a pair of headersthrough which refrigerant flows to and from said inner tubes.

9. In a refrigeration system which includes an evaporator upon whichfrost tends to accumulate, a com pressor, a condenser, and refrigerantlines connecting to' deliver hot refrigerant gas to said internalpassage ways, and restrictor means providing a flow connection from saidinternal passageways to said annular passageway's whereby liquid"refrigerant condensed within said internal passageway/sis delivered tosaid annular'pas'sageways" at areduced pressure.

10. Iri a 1fefrigeration system of the charactefi de scribed;-refrigerant cdnde'nsingme'aiis' comprising coinpre's'sor means-aridcondenser means, airevaporatoras sembly comprising a plurality of tubeassemblies, each of which has an inner tube and an outer tube positionedconcentrically with an annular space therebetween and a fin constructionpositioned within said annular space and maintained in heat conductedrelationship with the outer surface of the inner tube and the innersurface of the outer tube, means to supply liquid refrigerant at areduced pressure from said condenser means to the annular spaces betweenthe inner and outer tubes of the respective tube assemblies, means todeliver refrigerant gas from said annular spaces to the intake of saidcompressor whereby said annular spaces act as the evaporator for thesystem, means to defrost said evaporator by supplying hot refrigerantgas from said compressor to the internal passageways formed by saidinner tubes whereby the heat from the compressed gas is transmittedthrough said inner tubes and said fin assemblies and thence through saidouter tubes and said refrigerant is condensed, and means includingrestrictor means to deliver the liquid refrigerant from said inner tubesto said annular spaces at a reduced pressure whereby the liquidrefrigerant is re-evaporated and delivered back to said compressor.

11. In apparatus of the character described, the combination of, anevaporator assembly comprising a plurality of tube assemblies each ofwhich comprises a plurality of concentrically positioned tubes andannular fin means therebetwecn, each of said fin means being in goodheat conducting relationship with the walls between which it ispositioned, said evaporator assembly including connecting meansinterconnecting each passageway through each tube assembly with thecorresponding passageways in the other tube assemblies thereby to form aplurality of concentrically positioned refrigerant passageway circuits,means to supply liquid refrigerant at a reduced pressure to one of saidrefrigerant passageway circuits and to withdraw gaseous refrigeranttherefrom, means to supply hot refrigerant gas to one of saidrefrigerant passageway circuits during a defrosting operation thereby toraise the temperature of the various tube assemblies and to condense therefrigerant, means to pass the refrigerant thus condensed at a reducedpressure through another of said refrigerant passageway circuits wherebythe liquid refrigerant is i e-evaporated.

12. In a refrigeration system, the combination of, a compressor having alow pressure inlet and a high pressure outlet, a condenser connected tosaid high pressure outlet, an evaporator having a plurality ofevaporator passageways and a plurality of defrosting passageways, saidevaporator including heat conducting wall means and heat transfersurfaces providing heat transfer relationship between said evaporatorpassageways and air being cooled at surface temperatures whereby frosttends to accumulate, said defrosting passageways extending substantiallyparallel with said evaporator passageways, said evaporator includingheat conducting means between said defrosting passageways and saidevaporator passageways which includes said heat conducting wall meansand which transmits heat from said defrosting passageways to said heattransfer surfaces thereby to defrost said surfaces, meansincluding'pressure reducing means connecting said evaporator passagewaysto receive liquid refrigerant from said condenser at reduced pressure,means connecting said evaporator passageways to said low-pressure inletof said compressor thereby to provide for the evaporation of refrigerantin said evaporator passageways, and defrosting means comprising meansforming a bypass circuit from said high pressure outlet of thecompressor to said defrosting passageways and thence from saiddefrosting passageways to said evaporator passageways, said bypasscircuit including a normally closed valve which is opened to permit hotgas to flow through said bypass circuit, said system including meansproviding a drop in pressure of the refrigerant flowing from saiddefrosting passageways to said evaporator passageways, whereby theopening of said valve delivers 8 hot refrigerant gas'to said defrostingpassagewaysand thereby defrosts said heat transfer surfaces and therefrigerant then passes at a reduced pressure into said evaporatorpassageways and is returned to said low pressure inlet of thecompressor.

References Cited in the file of this patent UNITED STATES PATENTS2,059,992 Gould Nov. 3, 1936 2,080,358 Kucher May 11, 1937 2,128,386Warren Aug. 30, 1938 2,611,585 Boling Sept. 23, 1952 2,611,587 BolingSept. 23, 1952 2,688,850 White Sept. 14, 1954 2,759,339 Kundert Aug. 21,1956 FOREIGN PATENTS 676,924 Great Britain Aug. 6, 1952

